Train problem

is this your train?

http://www.lionel.com/products/finder/ProductDetail.cfm?ProductNumber=6-30123&expandBranch=0&Keywords=&CategoryID=455&RailLineID=&CatalogId=

track could have dirty spots.  these engines do not smoke that good unless the train is long or going very fast.  you might try running wires from the transformer to the spot where it slows down.  the fastrak has male blades on the bottom to add wire drops.  do you have a club close by you could go and run the train there?

others will have more to say.

If you bought it at a local hobby/train store, I would take it in for them to run on their track and/or examine it.  It should work much better than that.  If still under warranty it can be returned to Lionel, also.